1]No,now he is no longer a sceptical.
2]No, he has never won the Tour de France
3]Yes , he took the illegal substances. He told that he would had sworn on any Bible that he wouldn't had taken illegal substances , but when he entered the system,his opinion had changed and he had taken the illegal substances.
4] No he did not abandon the tour
1)No, he is no longer a professional cyclist.
2)Illegal substances mean here drugs
3)He is talking about the system of Tour de France
4)Opposite to word " professional" is a word "amateur"
5)Here "wearing" means :have clothes on your body
8)Maddening is formed from a adjective "Mad" by adding to it an ending "ing" .So, this word describes a person who is going mad .